This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:                3GPP third generation partnership project        BS base station        DL downlink (network towards UE)        eNodeB EUTRAN Node B (a BS in the LTE system)        E-PDCCH enhanced PDCCH        EUTRAN evolved UTRAN (LTE)        FDM frequency division multiplexing        LTE long term evolution        MAC medium access control        MIMO multiple input multiple output        MME mobility management entity        Node B base station (includes BTS)        PDCCH physical downlink control channel        PDSCH physical downlink shared channel        PRB physical resource block        PUSCH physical uplink shared channel        RB resource block        RE resource element        RF radio frequency        RS reference signal        TDM time division multiplexing        UE user equipment        UL uplink (UE towards network)        UTRAN universal terrestrial radio access network        
The LTE system is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. In the LTE and other cellular radio systems the base station (termed an eNodeB or eNB in LTE) signals the time-frequency resources allocated to a mobile terminal (UE). In LTE the downlink and uplink resources are allocated via the PDCCH in terms of RBs. The number of RBs available in a time slot depends on the bandwidth and varies from 6 to 100, corresponding to bandwidths of 1.25 and 20 MHz respectively.
In LTE there is frequency selective scheduling for the DL and UL shared data channels (PDSCH and PUSCH) in order to allocate the best RBs for each terminal. This gives the best performance but is also the most expensive in terms of signaling. While this scheduling technique allows advanced multi-antenna techniques like precoded transmission and MIMO operation for the downlink shared data channel, currently the user specific downlink control signaling on the PDCCH does not employ any of these gaining mechanisms (e.g., frequency domain scheduling gain, advanced multi-antenna gains). To improve the PDCCH multiplexing capacity as well as to exploit some of these gaining mechanisms the 3GPP organization has initiated a study item for enhanced downlink control signaling using UE-specific reference signals enabling enhanced multi-antenna transmission also for the user specific DL control channel.
LTE is a heterogeneous network, in which there are access nodes apart from the traditional BSs which operate at different power levels. For example, there may be privately operated femto nodes to which the conventional (macro) eNodeBs can offload traffic; and/or there may be remote radio heads or repeaters to fill coverage holes. Heterogeneous networks are susceptible to widely varying interference, and LTE introduces a new logical channel E-PDCCH.
FIG. 1 is a block diagram illustrating the radio environment and the relevant logical channels in LTE. There is a MME 16 which interfaces multiple eNodeBs 14 to the Internet or other broader communication network, and the eNodeB 14 communicates with on the UE 10 under its control over the wireless interface. The control information from eNodeB 14 for UE 10 is carried on the PDCCH and/or the E-PDCCH, including resource allocations etc. The E-PDCCH is relevant since if the UE has an allocation in the DL the allocated PDSCH resources might lie in a same RB where the E-PDCCH is sent. Further detail in this regard is shown below with respect to FIGS. 2A-B and 3. Considering that radio spectrum is a scarce resource, it is advantageous that the E-PDCCH and PDSCH can share the available RBs in a radio-efficient manner. The resources for the E-PDCCH might be already reserved for the PDSCH (according to LTE Release 8 to Release 10 specification), but currently there is no way for the UE which has the DL allocation for the PDSCH to know whether there would be a E-PDCCH transmission placed within its allocated PDSCH resources, either in that same RB or a RB within the PDSCH allocation).
The exemplary embodiments of the invention detailed below provide a means to improve the efficiency of the PDSCH granted by the E-PDCCH. While these examples are in the context of the LTE system to show more specific details of an LTE implementation, the broader teachings herein are readily applicable to any radio access technology in which the network signals radio resource allocations to UEs.